Datensatz

Zusammenfassung

The extracellular compartment of the brain is a complex, dynamic microenvironment containing nutrients, metabolites, and molecules related to neural signaling. Understanding of brain function requires direct monitoring of neural activity, commonly done by means of intracortical microelectrode recordings. The existing extracellular recording techniques provide us with rich information regarding single or multiple neuron activity as well as some information about subthreshold processes, but fail to reveal the role of inhibition in the anatomically demonstrated microcircuits. One possible solution to this is simultaneous extracellular field potential and neurotransmitter recordings. In this study, an in vivo nanosampling technique was developed, with significantly higher spatial resolution than that afforded through microdialysis. The technique capitalizes on its ability to directly withdraw large quantities (several hundreds of nL) of extracellular fluids (ECF) from the monkey brain at a rate of 1-50 nL min-1. The fluids were stored along a 4 m long, 20 µm I.D., 90 µm O.D. fused silica capillary loop. The obtained intact ECF sample was then distributed into a series of micro-vials according the time interval specified by the system’s temporal resolution. The contents of multiple neurotransmitters and signaling molecules in each distributed ECF sample, including glutamate, GABA, acetylcholine, and asparagine, were determined simultaneously by capillary HPLC-MS. Hydrophilic interaction chromatography was employed to separate the highly polar and ionic compounds directly for mass spectrometer detection.